This paper describes the effort to develop a pipeline concept as a
substitute for conventional pipelines that lie on the seabed. A submarine
pipeline in a submerged floating tunnel (SFT) is presented as a potential way
to avoid pipeline-related environmental concerns. The key task in developing
this submarine pipeline concept is to integrate solutions to the environmental
challenges associated with submarine pipelines into the SFT structure.

From a technical standpoint, one of the most
important design tasks is to calculate the SFT’s buoyancy weight ratio (BWR) value, thereby
determining the tunnel’s stability. The greatest threat to
stability is the phenomenon of tether slack, which
occurs at a specific BWR value. The pipeline’s weight affects its BWR
value, so the weight must be restricted to ensure that tether slack does not
occur. In the present study, the proposed SFT’s BWR value was simulated by
testing a laboratory model in various ballasts. Significant waves and individual waves in a
hundred-year return period were investigated based on data related to Java Sea waves at the Indonesian Hydrodynamic
Laboratory (IHL).

This study
tested the SFT laboratory model against regular waves to find the BWR value at
which tether slack might occur. The obtained BWR value was used
to determine the requirement for total pipeline
weight. Using a 1:100 scale of the real environmental conditions, the laboratory
results revealed that slack occurs in a significant wave when the BWR value is
1.2, making the maximum pipeline weight to be placed in the SFT 534 tons. For
the individual wave, slack occurs when the BWR value is 1.4, making the maximum
pipeline weight to be placed in the SFT267.214 tons.